Conventionally, JP-A-3-291465 discloses a refrigerant cycle device including an ejector. In the refrigerant cycle device as disclosed in JP-A-3-291465, a vapor/liquid separator for separating refrigerant into liquid and vapor phases is disposed on the downstream side of the ejector. The vapor/liquid separator separates the flow of refrigerant into one flow which is to be sucked into a compressor, and the other flow which is to be sucked into a refrigerant suction port of the ejector.
A first evaporator is disposed between the vapor/liquid separator and the compressor, and a throttle device and a second evaporator are disposed between the vapor/liquid separator and the refrigerant suction port of the ejector. Both evaporators exhibit a heat absorption effect of the refrigerant. At this time, the effect of decompression by the throttle device lowers a refrigerant evaporation pressure of the second evaporator (refrigerant evaporation temperature) as compared to that of the first evaporator, so that the refrigerant can evaporate in different temperature ranges at both the evaporators.
When the refrigerant cycle device as disclosed in JP-A-3-291465 is actually actuated, the second evaporator may be operated without exhibiting a refrigeration capacity. The inventors have studied about the cause for this problem, and found that the problem is due to arranging a throttle device on the upstream side of the second evaporator. The reason for this is that the decompression and expansion of the refrigerant by the throttle device results in a loss of kinetic energy of the refrigerant, so that a dynamic pressure of the refrigerant after the decompression and expansion is decreased as compared to that of the refrigerant before the decompression and expansion.
That is, when the dynamic pressure of the refrigerant after the decompression and expansion is decreased, the dynamic pressure at the outlet of the ejector cannot be applied to refrigerant on the downstream side of the throttle device. As a result, a pressure difference between a static pressure of the refrigerant on an outlet side of the throttle device and a static pressure of the refrigerant on the refrigerant suction port of the ejector has to cause the refrigerant on the downstream side of the throttle device to flow into the second evaporator.
When the vapor/liquid separator is disposed on the upstream side of the throttle device, like the cycle as disclosed in JP-A-3-291465, the separation of the refrigerant into the liquid and vapor phases at the vapor/liquid separator also results in the loss of the kinetic energy of the refrigerant with little dynamic pressure of the refrigerant after the decompression and expansion. Thus, only the pressure difference between the static pressure of the refrigerant on the outlet side of the throttle device and the static pressure of the refrigerant on the refrigerant suction port of the ejector needs to allow the refrigerant on the downstream side of the throttle device to flow into the second evaporator.
Thus, even in operating the cycle as disclosed in JP-A-3-291465, when a loss of pressure between an inlet and an outlet of the second evaporator is larger than the pressure difference between the static pressure of the refrigerant on the outlet side of the throttle device and that of the refrigerant at the refrigerant suction port of the ejector, the refrigerant is not allowed to flow into the second evaporator. As a result, the second evaporator may not obtain the refrigeration capacity.